Refrigerating apparatus



mg; 18, 3945, c; LOUTHAN 2,391,252

REFRIGERATING APPARATUS Filed June 12, 1944 s Sheets-Sheet s I INVYIENT .2 w, M

Patented Dec. 18, 1945 2,391,252 REFRIGERATING APPARATUS Chester F. 'Louthan. Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application June 12, 1944, Serial No. 539,840

1 Elalm.

This invention is one specific aspect-is related to refrigerating apparatus and heat exchangers, but more particularly relates to a method of and apparatus for forming metal such as sheets, plates, tubing and hollow pieces of material.

In the past, many methods and forms of apparatus have been used for forming sheet metal,-.

plates, tubing and hollow pieces of material. Some examples of methods for forming are pressing, drawing, simple bending, spinning, rolling and swaging. Each has its advantage and disadvantages, but in general these methods are slow and expensiveand limited in the amount of shaping or deformation accomplished.

It is an object of my invention to provide a new method of forming hollow articles which is very rapid and inexpensive.

it is another object of my invention to provide a new method which can form materials in a wide variety of shapes.

It is another object of my invention to provide a method of and apparatus for providing greater deformation in forming materials.

It is a specific object of my invention to provide an improved method of and apparatus for providing fins upon tubing.

These objects are attained generically by applying force to the walls and by applying heat simultaneously or instantaneously orv both, to the portion of the walls which are to be deformed or shaped. More specifically the forming or shaping is accomplished by applying either a hydraulic or mechanical force or both to the thin .walls, accompanied by instantaneous heating limited to the portion of the walls to be deformed, and mechanically confining the extent of the deformation. This heating is most conveniently provided by passing alternating current of suitable potential between electrodes in contact with separated points upon the portion.

of the walls to be deformed.

.Further objects and advantages of the present an apparatus ready to carry out a method for further deforming the tubing;

Fig. 4 is a diagrammatic sectional View similar to Fig. 3 showing the apparatus at the completion of the second deforming operation;

Fig. 5 is an apparatus shown ready to carry out another application of my new method;

Fig. 6 is a diagrtlc view similar to Fig. 5, showing the apparatus at the completion of the operation;

Fig. 7 is a sectional view taken along the line 1-1! of Fig. 5; s

Fig. 8 is adiagrammatlc view 1' to Fig. 5,, showing a modified form of the apparatus shown in Figs. 5 to 1;

Fig. 9 is a diagrammatic view similar to Fig. 1 showing an apparatus ready to form a projection on each side 01 a sheet fin;

Fig. 10 is a view similar to Fig. 9, showing the apparatus at the completion of the iorming opv eration; and

Fig. 11 is a sectional view taken on the line H-li of Fig. 9.

One application of my invention is the forming of annular folds or projections in the walls of tubing. Such a structure may be used to provide greater heat transfer area within a given space, or it may be used as a bellows. In Fig. 1, thereis shown an apparatus for carrying out one form of my invention for providing a series of annular projections or folds in the walls of tubing. In this apparatus there is a normally stationary part 20 provided with a, flange 22 containing a large vertical aperture 24. Supported upon the flange 22 is a normally stationary split clamping means in the form of a stationary block 26 fastened by the screws 28 to the vertical portion 30 of the member 20 and a removable block 22. The tubing 28 is received in recesses iormed in the adjacent, portions of the clamping blocks 26 and 22. The clamping blocks are held in clamping relationshipwith the tubing 28 by the long screws 24 located on opposite sides of the recesses receiving the tubing 36. These long screws 24 extend through the block 22 and thread into the block 26. By this arrangement this portion of the tubing 22 is firmly held in place.

Above the stationary'block 28 is a movable block 22 having flanges interfitting' with a vertical T-slot slideway 40 provided upon the vertical wall portion of a stationary member 42 which is insulated from the member 20 by the insulating means 44,. The portion of the tubing above the blocks 28 and 32 is clamped between lower end of a piston rod 50 shown diagrammatically, which is part of the apparatus used for raising or lowering the blocks 38 and 46, providing a force in their direction of movement.

The piston rod 50 is shown connected to a piston 52 within a pressure cylinder 54 provided with a compression spring 58 for raising the piston 52 to the top of the cylinder. There is also shown diagrammatically a system for moving the piston 52, rod 50 and the blocks 68 and 88 downwardly for applying an axial force to the portion of the tubing between the two sets of clamping blocks. Preferably this comprises either a liquid or air pressure system, and includes a pressure pump together with means for applying and releasing the pressure. For example, there is and the amount and duration of the heating of the portion of the tube 36 between the sets of clamping blocks.

For example, with steel tubing having a 0.035" wall I used water pressure from 1800 to 2100 lbs. per square inch. I had used higher pressures but if pressures are too high there is danger that the tubing will burst. With this tubing and pressure I have used various distances between the clamping blocks, such as. and of an inch. I find that the projections are much smoother if well rounded fillets 94 and v 86 are provlded'at the ends of the apertures proshown diagrammatically a sump 88, a pump 60,

a pressure reservoir 62 and a three-way valve 64 which connects the pressure reservoir 62 with the cylinder 56. The three-way valve til can also connect the cylinder 56 with the sump 58 to release the pressure on the cylinder. Suitable conduit means connect the members of the hydraulic system. A gauge 65 is provided to indicate the pressure within the cylinder so that the threeway valve 86 may be manipulated in order to apply the proper pressure to the cylinder to provide the proper axial force on the tubing between the two sets of clamping blocks.

The upper end of the tube 86 may extend up beyond the clamping blocks 38 and 66 as far as is desired. The end should be plugged by any suitable means, such as a cap 68 with a flare clamping gland iii. The lower end of the tubing 36 which may also be as long as desired is provided with a flare connection 72 which connects the interior of the tube 38 with another hydraulic system. This second hydraulic system includes a sump id, a pump it, a three-way valve 18, a gauge 58, a simple hand valve 82 and suitable connections connecting the elements to gather and connecting through the flare connection 82 with the-interior of the tube 36.

There is also provided means for instantaneously heating the portion of the tubing between the twosets of clamping blocks. This includes a suitable transformer 34? connected to a suitable alternating current power supply.- A transformer, such as is used for projection, roll and spot electric welding may be used. One of the low voltage output terminals of the transformer 8% is connected by the conductor 88 to the member 29 while the other terminal is connected by the conductor 88 to the movable block 38. The switch at is connected into the primary circuit of the transformer for controlling the energization of its secondary circuit.

Incarrying out my new method with this ep blocks, the axial force applied by the piston 52 vided in the sets of clamping blocks. 1 have shown the surfaces of the clamping blocks flared around the apertures for the purpose of forming a sloping wall on the projections. The contour of these-surfaces may be varied so as to secure difierent shapes of side walls as may be desired. For example, by leaving the adjacent faces of the sets 01' clamping blocks perfectly straight the walls of the projections will be straight. Also these surfaces may be made with annular beads or other formations in order to produce corresponding shapes.

After the tubing is clamped and the hydraulic pressure is applied within the tubing, the upper hydraulic system is manipulated so as to apply the proper pressure'within the cylinder 56 to secure the desired axial pressure on the portion of tubing between the sets of clampingblocks. With the type of steel tubing'mentioned previously I prefer to use an axial pressure of 1000 to 1250 lbs. which represents20 lbs. to 26 lbs.

, gauge pressure on the gauge 66 when the area of the piston 52 is 50 square inches.

After this is done the switch 90 may be closed for a very short interval. I prefer to use a 125 kva. transformer at 8 volts for two alternating current cycles, providing two successive surges of current estimated at 20,000 amperes. However, I have successively performed by new method with various voltages at from one-half to 5 alternating current cycles with such a transformer. During this very short time, A of a second, the portion of the tube between the sets of clamping blocks is heated and softened and expands in diameter and at the same time the upper set of clamping blocks move downwardly under the axial force provided by the pressure on the piston 52 until the upper set of clamping blocks and the upper portion of the tubing reach the position shown'in Fig. 2 forming the projection as between the two sets of blocks. The lower set of clamping blocks is provided with a suitable annular recess H which receives the previously formed annular projection. If desired- .eei as this type properly positioned are provided in lower set of clamping blocks.

The aperture 23d inthe ge 22 is made sum-- n ly largeto wodate previously formed projections located below the lower set of clamping bl.

After such a projection, such as the projection 98, is formed, the screws 36 and-(l8, are removed and the tubing is lowered so that the projection 98 moves into the recess till after which these screws may again be inserted the oping blocks fastened and a second projection may be formed in a similar manner. By employing auto matlcally opening and closing ping bloom and automatic means for I ing the tubing when the blocks are separated and by automatically closing the switch 98 at the proper time, the tubing may be rapidly made by sure within the tubing.

this method requiring only the work of an operstar to remove a finished piece and to insert a new piece. By this arrangement such projections maybe formed on tubing rapidly and inexpensively. These projections can be provided in much smaller tubing than projections could be provided by other means and the projections may be made larger than by other means. Smaller projections may be made without internal pres- .jections such as may have been formed by the apparatus shown in Figs. 1 and 2.

Above the third projection is another stub-end of tubing which fits within the bottom face of a piston III. This piston Ill operateswithin the cylinder 3 which contains the piece of tubing l2l provided with the three projections and the stub ends; This cylinder H9 is insulated from the metal base member I and the slide member I I3 by the insulating means 123. In the form of method used with this apparatus no pressure is provided within the piece of tubing I. The piston III is connected to a piston rod similar to the piston rod 50 which is provided with a piston within a cylinder connected to a hydraulic system such as is provided in Fig. 1. This arrangement is used to provide the desired axial pressure upon the piece of tubing l2l.

A suitable welding type transformer I25 is provided and connected to a suitable alternating current power source. One of the low side terminals of the transformer I25 is connected by the conductor i2! to the metal base lll' while the other low side terminal is connected by the conductor I29 to the piston rod of the piston Ill. The switch i3! is connected in the primary circult of the transformer I25. When the proper axial force is provided in the manner suggested by the piston H1, theswitch I3| is closed for a short time such as one to five cycles of altemating current, and under such conditions the piece of tubing l2! will weaken between the projections and will collapse and be formed into the shape shown in Fig.4 in which the piston II! has moved downwardly as the piece l2! was heated and softened by the current flow. Such a construction provides a large amount of heat transfer area within a small space.

In Figs. 5 to 7 there is shown diagrammatically apparatus for carrying out another form of my method. In Fig; 5 there is shown a metal supporting block 202 provided with a semi-circular groove for receiving a section of the tubing 204.

At one end, this tubing 204 is sealed by a cap and flare connection 206, while the other end of this tubing is connected by the flared connection 203 to the tubing 2l0 which connects to a hydraulic system. This hydraulic system includes a sump 2|2, a pump 2I4, a three-way valve MS, a gauge M8 and a hand valve 220 for applying a suitable internal pressure andholding that pressure within the tubing 204. For example, water may be pumped into the tubing 204 and the tubing filled with the water at a selected pressure and sealed therein by the closing of the valve 220, as explained before.

At one end of the block 202 there is provided a stationary anvil 222 which is split into segments 224 and 226, as shown in Fig. 7. This anvil 222 is held stationary with respect to the block 202.

It is provided with asemi-circular groove ,228

which extends through an arc of 180 degrees on the periphery of the anvil. A movable roller 230 is provided with a similar groove 232 so that the tubing 204 will just fit in the grooves 223 and 232 between the anvil roller without distortion. The flanges on the roller 230 rest upon the flanges of the anvil 222 so as to prevent crushing the tubing 204.

A welding type of transformer 234 is provided which is connected under the control of a switch 240 to a suitable power source. One of the low voltage terminals of the transformer 234 is connected by the conductor 236 to the segment 228 of the anvil 222 while the other low voltage terminal of the-transformer 234 is connected by the conductor 238 to the segment 224 of the anvil 222. These two segments 224 and 226 are electrically insulated from each other by reason of the gap between them which may be filled with suitable electrical insulation.

In order to make a U-shape bend in a tube,

switch 240 is closed and the roller 230 which is located in the position shown in Fig. 5 at the start of the operation is rolled in a semi-circular path 23l in a counter-clockwise direction from this starting position along the flanges of the anvil so that the tubing is gradually rolled into the groove 223 provided in the anvil until the roller 230 haspassed 180 degrees around the anvil to the position shown in Fig. 6. During this movement of the roller 230, the hydraulic pressure and in particular the liquid, is sealed within the tube at the predetermined hydraulic pressure. The roller 230 forces the inner half of the tubing tightly against the adjacent portions of the anvil 222 to bridge the gap between the segments 224 and 226 so as to close the secondary electrical circuit which the transformer 234 feeds. This current passes through this portion of the tubing and heats the tubing so that the inner half of the tubing is heated and softened and allows the tubing to be formed into a U-shape without causing any appreciable flattening of the tubing in the bent portion.

In Fig. 8 there is shown a modification of the apparatus shown in Figs. 5 to 7; In this modification, the tubing, the hydraulic system and the supporting blocks are the same as in Figs. 5

I to 7. The anvil 322 is different in that it is made of one solid piece and is connected through the conductor 338 to one terminal of the transformer 334, the other terminal of the transformer 334 being connected by the conductor 336 to the shaft of the roller 330. The connection of the primary circuit of the transformer. 334 to the source of power is controlled by the switch 340. In this modification the roller 330 rolls the tubing into the groove of the anvil 322 in a manner just like that described for Figs. 5 to 7.

lection of materials to be used when tubing must forming of annular folds or projections on opposite sides of fins to clamp them to the tubing. One form of apparatus for carrying out this method is shown in Figs. 9 to 11. Generally speaking this apparatus is similar to that shown in Figs. 1 and 2 and includes a normally stationary part 420 provided with a flange 422 containing a large slot 424. Supported upon the flange 422 is a normally stationary split clamping means in the form of a stationary block 426 fastened by the screws 428 to the vertical portion 430 of the member 420. The stationary block 426 cooperates with a removable clamping block 432. The tubing 436 is received in recesses formed in the adjacent portions of the clamping blocks 426 and 432 and extends through the slot 424. The clamping blocks are held in clamping relationship with the'tubing 436 by the long screws 434 located on opposite sides of the recesses receiving the tubing 436. These long screws 434 extend through the block 432 and thread into the block 426. .By this arrangement this portion of the tube 436 is firmly held in place.

Above the stationary block 426 is a movable block 438 having flanges interfitting with a vertical T-slot slideway 440 provided upon the vertical wall portion of a stationary member 442 which is insulated from the member 420 by the insulating means 444. The portion of the tubing above the blocks 426 and 432 is clamped between the slidable block 438 and the movable clamping block 446 by the long screws 448 which extend through the block 446 and thread into the block 438. These two blocks are each provided with complementary halves of an aperture which receives the tubing 436. The blocks 438 and 446 are connected to the lower end of a piston rod 450, shown diagrammatically, which is part of the apparatus used for raising or lowering blocks 438 and 446 providing a force in their direction of movement. I

The piston rod 450 isshown connected to a piston 452 within the pressure cylinder 454 provided with a compression spring 456 for raising the piston 452 to the top of the cylinder. There is also shown diagrammatically a system for moving the piston 452, the rod 450 and the blocks 438 and 446 downwardly for applying an axial force to the portion of the tubing between the two sets of clamping blocks. Preferably this comprises either a liquid or air pressure system and includes a pressure pum together with means for'applying and releasing .the pressure. For example, there is shown diagrammatically a sump 458, a pump'460, a pressure reservoir 482 and a three-way valve 464 which connects the pressure reservoir 462 with the cylinder 454. The threeway valve 464 can also connect the cylinder 454v far as is desired. Above the clamping blocks 438 and 446 there rests a plurality of thin sheet metal .discs 6|! to be fastened as fins at spaced inter- Suitable conduit means connect the.

' cycles.

vals on the tubing 4416. Between the upper and lower sets of clamping blocks, one of such fins. 62L is supported by a resiliently mounted supporting member 523. This resiliently mounted supporting member 523 supports the fin 52] midway between the upper and lower set of clamping blocks when the blocks are separated as shown in Fig. 9. This resiliently mounted supporting member 523 is supported by upper and lower coil springs 525 and 521 which surround removable pins of electrical insulating material which fit into drilled apertures in the upper and lower sets of clamping blocks. Recesses' lined with electrical insulating material are provided in the clamping blocks for receiving the springs when they are compressed. The removable pins guide the resiliently mounted supporting member 523 in a vertical direction while the springs govern its location.

In clamping the fins to the tubing with this apparatus no hydraulic pressure is used within the tubing but an axial force is applied to the slidably mounted upper set of clamping blocks by the piston rod 450. Preferably this axial force provided by the pressure system is about 1000 to 1250 lbs. for steeltubing having a .035"

- wall. The secondary circuit of the transformer 484 is then energized for a brief interval such as two cycles by the closing and subsequent reopening of the switch 490 in the primary circuit of this transformer to cause a flow of low voltage current between the stationary clamping block 426 through the tubing 436 to the slidably mounted clamping block 430. This causes the softening of the walls of the tubing 436 between I the two sets of clamping blocks and causes projections or annular folds to form on each side of the fin 52! as shown in Fig. 10 between the two sets of clamping blocks. The fin 62! prevents the expansion of the tubing between the annular folds or projections. These annular folds or projections are pressed tightly between the clampmg blocks by reason of the axial pressure provided by the piston rod 450 thereby clamping the inner edges of the fin 62I tightly between the two projections. The switch 490 is only closed for one .or two alternating current The current and the voltage are preferably substantially the same as that set forth in the method described in connection with Figs. 1 and 2. For providing this size tubing with folds projecting about 1 5" from the straight walls of the tubing on opposite sides of the fin, the upper and lower sets of clamping blocks are set about apart and moved together until they are about Y apart. The lower set of clamping blocks is provided with suitably spaced recesses 50! for receiving the fins which previously have been attached to the tubing by the projections;

After one fin is attached to the tubing the clamping blocks are opened andv the tubing moved down until the last attached fin is placed in the uppermost recess in the lower set of clamping-blocks. At the same time the lowermost fin of the stack of fins its is moved down and placed upon the resiliently mounted supporting member 523, after which-both sets -of clamping blocks are clamped together. In removing the removable clamping blocks it may be necessary to remove two of the guide pins for the resilient supporting 'member 623 which must again be replaced before the blocks are again clamped together. The fins may be attached to the tubing successively in this manner. It should be understood that the examples disclosed herein are,

merely illustrative of a few of the many possible applications of the method and apparatus disclosed herein, which is believed to be almost unlimited as to the material to be worked upon and to the formation provided.

While the form of embodiment of the invention as herein disclosed, constitutes a. preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claim which follows.

What is claimed is asfollows:

portion. 10

The method of forming tubing which comprises, applying an internal pressure within the tubing, applying a. bending force to the tubing to bend the tubing through an angle and while under such force and internal pressure sending an electric current through that portion of the tubing at which the bending is desired to heat and facilitate the bending of the tubing at that CHESTER F. LOUTHAN. 

